Permanent anti-freeze liquid containing an anti-foam phase of a silicone in a mineral lubricating oil



PERMANENT ANTI-FREEZE LIQUID CONTAIN ING AN ANTI-FOAM hHASE OF A SILICONE IN A MINERAL LUBRICATING OIL Theodore C. Heisig, White Plains, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware N Drawing. Application August 25, 1956, Serial No. 376,533

9 Claims. (Cl. 252-78) This invention relates to polyhydric alcohol antifreeze liquids of the types adapted to be added to water or an equivalent'liquid in the circulating cooling system of an internal combustion engine or like device.

The invention is applicable to the various types of water-miscible polyhydric alcohols employed as freezing point depressants for water and equivalent liquids in circulating cooling systems. glycols such as mono and diethylene glycols and other glycols, polyglycols and glycerine. The preferred embodiment of the present invention employs mono ethylene glycol alone or mixed with diethylene glycol as the freezing point depressant.

In service, such anti-freeze liquids give rise to serious corrosion of the metals such as steel, brass, copper, aluminum, solder, and their alloys which they contact in circulating systems. Various corrosion inhibitors and inhibitor combinations have been employed in an eifort to overcome that difficulty. A number of such inhibitors and combinations thereof that have proven successful are disclosed in the copending application of William R. Smith, Serial Number 63,629, filed December 4, 1948, and entitled Anti-Freeze Liquids, now Patent No. 2,524,484, dated October 3, 1950.

A further difliculty encountered in the use of such anti-freeze liquids is foaming. In practice, it has been found that the water and anti-freeze mixtures foam at times to an extent to escape from the cooling system and seriously reduce the quantity of cooling fluid remaining in the system so that the engine or other device being cooled may become seriously overheated. While this foaming to a limited extent may be traced to the use of certain corrosion inhibitors, the principal causes appear to be the mechanical designs or plumbing of the cooling systems, the use of certain proprietary compounds in an effort to inhibit corrosion, the retention of small amounts of cleaning compounds in the cooling systems because of improper flushing, the circulating means in the cooling system, the radical changes in temperature of the cooling fluid, the trapping of air in heaters, etc., during periods of inactivity, and the leakage of air or other gases into the system. This is indicated by the inability to secure foaming of the cooling mixtures in laboratory tests and the subsequent foaming of the same mixtures in operation of certain engines.

Typical anti-foam mixtures or agents, such as are used in boilers and like places where mixtures of water and various chemical compound are found to foam excessively, have been tried in such cooling liquids and found unsuccessful. Other types of anti-foam agents have been tried and found difficult to dissolve or disperse or to stay in such dissolved or dispersed phases during use. The latter is a particularly difiicult problem with internal combustion engines such as are used in automobiles wherein there may be long periods of inactivity between periods of use.

It is an object of this invention to provide an antifreeze liquid wherein foaming is inhibted to an extent it Sttes Patent O Such alcohols include ethylene groups.

Patented Oct. 30, 1956 ICC? to substantially eliminate the foam problem despite any foam developing circumstances that may be encountered.

A further object of the invention is the provision of an anti-freeze liquid of the so-called permanent type wherein foaming is inhibited over long periods of service without the addition of more foam inhibiting agent.

Still another object of the invention is the provision of a novel method of combining an anti-freeze liquid with an anti-foam agent wherein the latter is placed in and remains in the resultant coolant. in an operative phase for substantially the entire effective life of the anti-freeze.

Other objects and advantages of the invention will appear from the following description taken in connection with the appended claims.

In brief, the present invention is directed to an antifreeze liquid having a water-miscible polyhydric alcohol base and an agent capable of inhibiting foam in the final coolant in which the anti-freeze liquid is incorporated. More specifically, the invention is concerned With an anti-freeze liquid incorporating a corrosion inhibitor or combinations thereof and an organo-silicon compound, preferably of the silicone type, the latter being present in sufiicient amount and in a phase such that it will inhibit foaming of the resultant mixture of the liquid with the water customarily used in a coolant system.

The water-miscible polyhydric alcohol, employed as a base for the anti-freeze liquid, includes such alcohols as ethylene, diethylcne and other glycols, polyglycols and glycerine. They should have a specific gravity greater than 1.0 so that the anti-foam phase having a specific gravity less than 1.0 will float.

Typical anti-foam agents include condensation pro ucts of organo-silicon oxides such as those condensation products containing a plurality of silicon atoms linked through oxygen atoms, each silicon atom having attached thereto at least one organic radical. Such compounds have come to be called silicones by reason of their containing the so-called silicone radical, i. e.

Such compounds may be formed by polymerization or condensation of organic silicols, the latter including mono-, di-, and tri-silicols as well as mixtures thereof.

Such compounds may be represented by the following formula:

in which n is one or more and R represents similar or dissimilar radicals such as alkyl, aryl, aralkyl, alkaryl or heterocyclic groups or the terminal Rs may be substituted by hydroxyl groups, or all but one of the Rs attached to the silicon atom may be substituted by bydroxyl groups or halides.

Such condensation products may be formed as straight chains, cyclic or cross polymerization products and may be liquids or solids.

Preferably R is a single organic radical of low molecular weight such as methyl, ethyl, and short chain alkyl Compounds having organic radicals of high molecular weight such as phenyls or compounds containing organic radicals of both high and low molecular weights, can be used.

A preferred compound is di-methyl silicone having the following formula:

in which n is one or more. In most cases, it is believed that the product contains a number of such polymers of different chain lengths and perhaps different chain types.

Such compounds are available in a wide range of viscositites, a viscosity in the range of 50 cs. (centistokes) to 1000 cs., and preferably a viscosity in the range of a proximately 100 cs. to 500 cs., being preferred.

Another class of organo-silicon oxide condensation products contemplated in practicing the invention are the organo-silicate condensation products represented by the following formula:

in which n is one or more and R likewise represents similar or dissimilar organic radicals such as alkyl, aryl, aralkyl, alkaryl or heterocyclic groups. Such compounds may be prepared by controlled or partial hydrolysis of the tetraorthosilicate esters with water. Again, organic radicals of low molecular weight such as methyl and ethyl are preferred although it is contemplated that radicals of higher molecular weights can be used alone or in combination with radicals of low molecular weight.

As the foregoing compounds and their methods of preparation are well known to the art and no claim thereto is made herein, further discussion thereof is considered unnecessary.

The preferred inhibitor combination, as disclosed in the aforesaid Smith patent, includes an alkali metal phosphate, an alkali metal silicate and mercaptobenzothiazole or an alkali metal salt of mercaptobenzothiazole, the latter being preferred over mercaptobenzothiazole. While the various alkali metal salts including those of sodium, potassium, lithium, etc., may be used, the sodium salt is preferred from the standpoint of availability and effectiveness. Where the sodium salt is referred to hereinafter, it is to be understood that the corresponding salts of the other alkali metals may be substituted therefor.

The sodium phosphate employed is the trisodium phosphase. Ordinarily the trisodium phosphate dodecahydrate (Na3PO4-l2H2O) is used. The sodium silicate, which is conveniently employed in the form of a concentrated aqueous solution, is preferably one having a high SiOz to NazO mol ratio in excess of 2.5:1, such as the well-known N brand of sodium silicate manufactured by the Philadelphia Quartz Company having a SiOz to NazO mol ratio of about 32:1. The mercaptobenzothiazole can be used in the form of a powder and dissolved in the glycol anti-freeze. The sodium mercaptobenzothiazole is preferably employed in the form of a concentrated aqueous solution of about 45-50% concentration, a commercial form of the material on the market being an aqueous solution containing about 46-47% by weight of the compound.

Based on laboratory and service tests, the proportions in which the various constituents of the inhibitor are employed are set forth in the following tabulation, together with a preferred example of each combination, the perclentalge being expressed by weight based on ethylene g yco Composition A Limits, Example, Percent Percent by Wt. by Wt.

Na3PO4.12H2O 1. 0-3. 5 2. 38 40 B. N Brand sodium Silicate So1ution 0. 8-1. 5 1. 0 50% Aqueous Solution of Sodium Mercaptobenzothiazole 0. 5-1. 2 0. 68

[Or expressed on a water-free basis in percent by weight based on ethylene The anti-freeze liquid containing either of the above combinations within the limit specified in a 40% concentration in water has a pH in excess of 9 and below 12, generally about 10.7-11.2.

In preparing the anti-freeze liquid of Composition A above, the trisodium phosphate dodecahydrate is first dissolved at an elevated temperature of 180-200 F. in a small amount of water. The sodium silicate and sodium mercaptobenzothiazole solutions are mixed therewith in the order mentioned. The quantity of water employed,

including the bound water of the phosphate and the free water in the silicate and mercaptobenzothiazole solutions, is preferably not substantially more than about the minimum required to maintain the said salts in solution at the elevated temperature, thus providing a nearly saturated aqueous solution at that temperature. A small flowing stream of the resultant aqueous solution, in controlled amount, is then admixed with a flowing stream of the alcoholic freezing point depressant, such as ethylene glycol, in controlled amount to provide about 3-8% by weight of the former to about 92-97% by weight of the latter in the resultant mix. This provides an anti-freeze liquid containing roughly about 2-5 by weight water based on the final anti-freeze liquid, and preferably about 3-4% total water. Actually, the amount of water initially added to dissolve the trisodium phosphate is much less than the figure specified above for total water and represents about 1-2% by weight based on the final antifreeze liquid. The small amount of water adds materially to the ease of preparation, and to the stability of the ultimate anti-freeze liquid on storage against sedimentation and salt separation and yet is so small as not to afiect the normal freezing point depressant properties of the ultimate anti-freeze liquid as compared to substantially pure ethylene glycol or other freezing point depressant. In compounding the anti-freeze liquid of Com position B above, the procedure is essentially the same except that the mercaptobenzothiazole powder must be separately dissolved in the glycol, preferably before mixing of the streams of aqueous solution and glycol.

In one typical method of preparing the anti-foam agent, a mixture of an organo-silicon compound such as dimethyl silicone of a viscosity of about cs. is prepared with an oil having a specific gravity in the range of 0.9 to 0.93, preferably between 0.9042 and 0.9218, the preferred slicone compound having a specific gravity of approximately 0.968. The oil is preferably of a naphthenic type having a fiash point (COC) of about 290 F. min. and 'a fire point (COC) of about 330 F. min., a viscosity at 100 F. (SU) of between 70 and 75 and a pour point of 35 F. max. The silicone in a foam inhibiting amount up to 2% by weight of the total antifoarn mix, is mixed with the oil. Silicone between 1 and 2%, desirably 1.5 is highly effective. However, very satisfactory foam inhibition at considerably lower cost has also been afforded, by much smaller amounts of silicone, such as 1 to 50 parts per million. The resultant mixture having a specific gravity less than 1.0 is added to the anti-freeze previously prepared in an amount between 0.90 and 1.25% by volume, an amount of about 1.05% by volume being preferred. It is obvious that the anti-foam phase may contain other materials such as corrosion inhibitors without materially affecting its novel anti-foam characteristics.

It will be understood that the resultng anti-freeze liquid is ordinarily mixed with 1 /2 times its volume of water forming a 40% solution for use in the northern zones of most temperate climates and with about four times its volume of water to form a 20% solution for use in the southern zones of such temperate climates. However, the liquid can be mixed with water in any proportion desired to provide the required freezing point according to freezing point tables, except that the glycol anti-freeze liquid should not be employed in a higher concentration in water than about 60%, because the more concentrated liquid becomes unduly viscouse at extremely low temperatures. This is typical of all glycol base anti-freeze liquids.

An oil of the character described is desirable as a vehicle for the silicone or equivalent anti-foam compound since it has no tendency to vaporize under radiator temperatures and has a specific gravity such that in the resultant mixture with the water or other coolant, there is little or no tendency for the anti-foam agent to settle or otherwise separate from the mixture in a manner such that it becomes ineffective. This is particularly important in internal combustion engines such as are used in automobiles wherein the engines may be subject to extremely hard usage at times with long rest periods in between, and the coolant is consequently subjected to alternate periods of vigorous circulation and rest.

A naphthene oil is preferred because of its ability to better emulsify with a water-glycol mixture. A naphthene oil is also advantage as compared with a paraffin oil since for the same viscosity, at naphthene oil is of a higher specific gravity and more miscible with the final coolant.

By reason of the specfic gravity of the oil being slightly less than that of the water anti-freeze mix, there is some tendency for some of the anti-foam mix to remain on the surface of the coolant. This is of advantage in that some of the mix is present in an effective position to break foam as soon as the latter attempts to form on the liquid surface.

The inhibitor combinations disclosed herein have proven unusually successful, the results of tests thereof being given in detail in the above-identied Smith patent to which reference is made.

The following has been found to be an especially effective anti-freeze liquid:

Percent by weight Ethylene glycol 94.6960 H2O (added) 1.4460 Na3PO.12H2O 2.2526 Sodium silicate 0.9488

Sodium mercaptobenzothiazole 0.6466

To the above, 1.05% by volume of anti-foam agent consisting of 98.5% by weight oil and 1.5% di-methyl silicone (100 cs.) is added.

The anti-foam agent has been found to be unusually successful in inhibiting foam and in continuing such property over the life of the anti-freeze. Its manner of association with the anti-freeze and cooling liquid mixture is such that the anti-foam is effective despite any long period of rest of the engine in which the coolant is used, thus making the anti-freeze particularly advantageous for engines used inautomotive vehicles.

This application is a continuation-in-part of my application Serial No. 84,259, filed March 29, 1949, now abandoned.

Obviously many modifications and variations of the invention as hereinabove set forth may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A two-phase permanent type anti-freeze liquid consisting essentially of a polyhydric alcohol phase containing 9297% by weight of a polyhydric alcohol having a specific gravity greater than 1.0 as the predominating constituent and a corrosion inhibitor soluble in the polyhydric alcohol, and 0.901.25% by volume based on the polyhydric alcohol phase of an anti-foam phase having a specific gravity less than 1.0 consisting essentially of a mineral lubricating oil insoluble in said alcohol having a specific gravity in the range of 0.9 to 0.93 containing dispersed therein a foam inhibiting amount up to 2% by weight based on the said anti-foam phase of an organo-silicon oxide polymer having antifoaming properties and selected from the group consisting of compounds having the formulas where R is selected from the class consisting of alkyl, aryl, aralkyl, and alkaryl groups, and n is a whole number of at least one.

2. An anti-freeze liquid according to claim 1, wherein the mineral lubricating oil is a naphthene base oil having an SUS viscosity at F. of 70-75, and a pour point of 35 F. maximum.

3. An anti-freeze liquid according to claim 1, wherein the polyhydric alcohol is at least one ethylene glycol having a specific gravity greater than 1.0.

4. An anti-freeze liquid according to claim 1, wherein the polyhydric alcohol is glycerine.

5. An anti-freeze liquid according to claim 1, wherein the organo-silicon oxide polymer is a liquid dihydrocarbon silicone polymer.

6. A two-phase permanent type anti-freeze liquid consisting essentially of a glycol phase containing 9297% by weight of at least one ethylene glycol having a specific gravity greater than 1.0 as the predominating constituent together with a small amount of dissolved water and corrosion inhibitor, and 0.901.25% by volume based on the glycol phase of a glycol-insoluble anti-foam phase having a specific gravity less than 1.0 consisting essentially of a glycol-insoluble naphthene base mineral lubricating oil having a specific gravity in the range of 0.9 to 0.93 containing dispersed therein a foam inhibiting amount up to 2% by weight based on the said antifoam phase of a liquid dimethyl silicone polymer.

7. A method of preparing a two-phase permanent type anti-freeze liquid which comprises forming a first predominating phase by dissolving corrosion inhibitor in a polyhydric alcohol having a specific gravity greater than where R is selected from the class consisting of alkyl, aryl, aralkyl and alkaryl groups, and n is a whole number of at least one; and then combining said first and second phases in proportions such that the resulting antifreeze liquid consists of 0.90-1.25 by volume of said second phase floating on said first phase.

8. A method of preparing a two-phase permanent type anti-freeze liquid which comprises forming a first phase by dissolving corrosion inhibitor in at least one glycol selected from the group consisting of ethylene glycol and diethylene glycol in proportions such that said first phase contains 92-97% glycol by Weight; forming a second phase by dispersing a foam inhibiting amount up to 2% by Weight of liquid dimethyl silicone polymer in a glycolinsoluble mineral lubricating oil consisting essentially of a naphthene base oil having a specific gravity in the range of 0.9 to 0.93 to form an anti-foamant; and then combining said first and second phases in proportions such that the resulting anti-freeze liquid consists of 0.90- 1.25% by volume of said second phase floating on said first phase.

9. An anti-freeze liquid according to claim 1 wherein said organo-silicon oxide polymer is present in an amount between 0.0001% and 2% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 2,416,504 Trautman et al. Feb. 25, 1947 2,435,124 Bollinger Ian. 27, 1948 2,467,177 Zimmer Apr. 12, 1949 

1. A TWO-PHASE PERMANENT TYPE ANTI-FREEZE LIQUID CONSISTING ESSENTIALLY OF A POLYHYDRIC ALCOHOL PHASE CONTAINING 92-97% BY WEIGHT OF A POLYHYDRIC ALCOHOL HAVING A SPECIFIC GRAVITY GREATER THAN 1.0 AS THE PREDOMINATING CONSTITUENT AND A CORROSION INHIBITOR SOLUBLE IN THE POLYHYDRIC ALCOHOL, AND 0.90-1.25% BY VOLUME BASED ON THE POLYHYDRIC ALCOHOL PHASE OF AN ANTI-FOAM PHASE HAVING A SPECIFIC GRAVITY LESS THAN 1.0 CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL INSOLUBLE IN SAID ALCOHOL HAVING A SPECIFIC GRAVITY IN THE RANGE OF 0.9 TO 0.93 CONTAINING DISPERSED THEREIN A FOAM INHIBITING AMOUNT UP TO 2% BY WEIGHT BASED ON THE SAID ANTI-FOAM PHASE OF AN ORGANO-SILICON OXIDE POLYMER HAVING ANTIFOAMING PROPERTIES AND SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS HAVING THE FORMULAS 